From Trimers to Chains: Growth and Defect Dynamics in Anisotropic Tellurium Films

Thin films of tellurium (Te) are fundamentally built from one-dimensional (1D) helical atomic chains, and they exhibit semiconducting properties that are tunable with dimensionality. The repeating structural motif within these chains is a triangular arrangement of three Te atoms, termed a trimer, which contributes to the overall helical geometry. Using scanning tunneling microscopy (STM), we investigated the layer-dependent changes in the electronic structure of these trimer units. In monolayer and bilayer Te grown on Au(100), we observed defects characterized by multiples of trimer vacancy clusters. In contrast, for thicker films such isolated trimer vacancies are replaced by 1D chains of missing row atoms or 1D edge dislocations. The propensities to form such vacancies and edge dislocations contribute to p-type semiconducting characteristics. These defects are segregated at the surface, and atomic layer deposition (ALD) of amorphous Al2O3 on the surface was found to induce surface transfer doping that converted the p-type to n-type characteristics.